Synthesis of silver nanoparticles in aqueous solutions in the presence of poly-N-vinyl-2-pyrrolidone

The synthesis of non-spherical silver nanoparticles (SN) was carried out in the presence of poly(N-vinyl-2-pyrrolidone) (PVP). Spherical SN were synthesized in aqueous solutions by reduction of silver nitrate by NaBH₄ at room temperature in aqueous solutions. The colorless solution gets color and the absorption band at 400 nm was registered. The system was irradiated in the visible and UV regions. In two hours of irradiation the long-wavelength band at 497 nm appears. It disappears after stirring the solution (in contact with air) and it is being restored upon subsequent UV irradiation confirming that the redox process plays the key role. After 2 days of irradiation the band shifts up to 624 nm and becomes resistant to stirring. Prismatic SN were isolated from the solutions after the long-term exposition. It was shown by IR-spectroscopy that PVP is associated with the SN surface in some way.